2005: IVA-1D
2010: 2A
Priority: Medium
(2010 Version)
2A. Investigation. Characterize potential key resources to support In Situ Resource Utilization (ISRU) for eventual human missions.
Key resources to support a human stay at the martian surface are C, O, and H for both life support and ascent propellant (see DRA 5.0). A key trade is the mass, power, and risk of the equipment needed to acquire and process these three commodities from martian resources compared to the mass, power, and risk of simply delivering them from Earth. One of the outcomes of the DRA 5.0 analysis was that in the case of C and O, the chemical pathways and processing equipment needed to obtain these commodities from the martian CO2 atmosphere are so well understood and simple enough mechanically that it makes excellent sense to plan for obtaining them via ISRU. For example, this could be used to supply breathing oxygen for the crew. Since the martian atmosphere is well-mixed, it is close enough to isochemical that no advance measurements are needed.
In the case of hydrogen (or equivalently, water), ISRU has the potential to have a substantial impact on mission affordability (particularly affecting the amount of mass to be delivered to the surface) especially for long-stay missions. Information from MGS, Mars Odyssey, MEx, MER, Phoenix, MRO and telescopic observations have shown that H resources exist on Mars in at least three settings of potential interest for ISRU (in hydrated minerals in rocks and soils, in ground ice, and in the atmosphere). However, it is not yet known whether the attributes of any of these resource deposits, coupled with the demands on the mission of the processing system needed to extract them, are compatible with a human mission’s engineering, risk, and financial constraints.
At this time it is not known where on Mars human exploration may occur. However, a key implication is that delivery of high-mass ISRU processing equipment to a single site on Mars would likely cause future missions to return to the same site. Returning to a single site may not be in line with mission objectives and this must be taken into account.
As is true of all extractive natural resources, determining whether a resource deposit is “ore” or “waste” cannot be determined without knowledge of BOTH the resource and the processing system. Reaching a future decision on whether H-ISRU should be a part of a human mission scenario therefore requires characterization of the candidate resource deposits at Mars (in addition to technology development work at Earth). The logic of the Mars characterization question is best approached in two sequential levels of detail: Phase I). Reconnaissance-scale characterization sufficent to make prioritization decisions, and Phase II). Detailed site-specific characterization sufficient to plan for specific mission design.
For H-ISRU to be properly considered and possibly incorporated into a future version of the reference architecture, the following measurements of H resources are needed. These resource types were prioritized based on our current perceptions of potential. Note that subsurface liquid water and subsurface gas hydrates/clathrates were considered as potential H resources, however a) these theorized deposits have not yet been identified and b) their likely depths exceed ISRU access capabilities. Thus no measurements of these resource types are called for at this time. Additionally, perchlorate was considered as a possible oxidant for manufacturing of ascent fuel. However, given that 1) a more readily available oxidant exists from the martian atmosphere (O2 extracted from CO2) and 2) there is no known method of unambiguously detecting perchlorate from orbit, no measurements of perchlorate are called for at this time.
ISRU-related precursor measurements were prioritized as follows: 1) mission design impact—major; 2) risk reduction – loss of mission.
1. Hydrated minerals. Numerous deposits of hydrated
silicate and sulfate minerals have been identified on Mars from spectroscopic
measurements [e.g., Bibring et al. 2005]. These deposits are attractive
candidates for ISRU because 1) they exist at the surface and therefore their
spatial distributions are easy to constrain using remote methods, 2) they exist
in a variety of locations across the globe and therefore provide many choices
for mission landing sites, and 3) the low activity of water in these minerals
precludes planetary protection issues. Limitations on existing measurements
include: 1) uncertainty of volume abundance within the upper meter of the
surface, 2) best available spatial resolution (~20 m/pixel) may not be
sufficient for ISRU processing design, and 3) mechanical properties of H-bearing
materials are not sufficiently constrained.
2. Subsurface ice.
Accessible, extractable hydrogen is likely at most high-latitude sites in the
form of subsurface ice [Boynton et al., 2002; Feldman et al. 2002; Mitrofanov et
al. 2002]. In addition, theoretical models predict subsurface ice in some
mid-latitude regions, particularly on poleward facing slopes [Aharonson and
Schorghofer, 2006]. Indeed, ice at northern latitudes as low as 42° has been
detected in fresh craters using high resolution imaging and spectroscopy. Based
on observed sublimation rates and the color of these deposits, the ice is
thought to be nearly pure with <1% debris concentration [Byrne et al. 2009].
Pure subsurface ice and other ice-cemented soil were also detected by the
Phoenix mission [Smith et al., 2009]. Clearly subsurface ice deposits have ISRU
potential, but are ranked lower than deposits of hydrated minerals because 1)
low-latitude ice deposits are currently thought to exist only in glacial
deposits that are associated with high elevations and difficult topography, and
2). Mid-latitude deposits have substantial overburden that would make mining
difficult (and in some cases are also in areas of difficult topography).
3. Atmospheric H-bearing trace gases (such as methane/H2O gas seeps and
transient ground fogs of water). Elevated concentrations of transient
methane have been observed in specific regions of Mars, suggesting the
possibility of methane gas seeps [Mumma et al., 2009]. At the Phoenix landing
site, ground-level water ice clouds were observed to form via sublimation in the
early morning hours and would dissipate during the day [Whiteway et al., 2009].
These types of localized, elevated concentrations of H have ISRU potential.
These are ranked lower than hydrated minerals and subsurface ice because 1) it
may be challenging to find concentrations high enough to satisfy mission H needs
alone, and 2) they may only occur in limited areas and would therefore limit
landing site choices. However, clearly more observations are needed to
substantiate or refute these claims and to evaluate their ISRU potential.
To more confidently evaluate the excavatibility, overburden,
and mission power/volume needs associated with each of these H-resource types,
additional reconnaissance is needed. At the site chosen for landing, in-situ
measurements to confirm the resource abundance with depth, excavatibility and
power needs for processing the H-resource(s) are required. Thus the following
measurement specifications are divided into intial reconnaissance and follow-up
in-situ measurements at the candidate landing site.
Hydrated minerals
a. High spatial resolution
maps (~2 m/pixel) of mineral composition and abundance. ISRU power estimates
depend on mineral composition because of the different heating needs to extract
water from each mineral type. The 2 m spatial resolution is based on that used
for terrestrial mineral prospecting, which is achieved using a combination of
high-resolution (2.5 m/pixel) visible imagery, lower resolution multispectral
imagery (15-90 m/pixel), and ore formation models. This spatial resolution
could potentially be achieved on Mars using existing sensors by combining
highest-resolution visible imagery (~50 cm/pixel) with highest-resolution
spectral data (~18 m/pixel). Assumptions of similar surface textures/albedos
between resolutions would be required using this technique.
Subsurface ice
a. High spatial resolution maps (~100 m/pixel)
of subsurface ice depth and concentration within approximately the upper 3
meters of the surface.
Atmospheric H-bearing trace gases
b.
Higher spatial resolution maps (TBD resolution) of H-bearing trace gases.
c. Assessment of the temporal (annual, seasonal, daily) variability of
these gases.
a. Verification of mineral/ice volume abundance and physical
properties within approximately the upper 3 meters of the surface. If the
H-resource is a mineral deposit, mineral identification must also be
verified.
b. Measurement of the energy required to excavate/drill the
H-bearing material
c. Measurement of the energy required to extract water
from the H-bearing material.
Review of this analysis by the Space Resources Roundtable is gratefully acknowledged.
Additional Information:
Aharonson, O., and Schorghofer, N., 2006, Subsurface ice on Mars
with rough topography:
Journal of Geophysical Research-Planets, v. 111,
E11007, doi:10.1029/2005JE002636.
Bibring, J. P., Langevin, Y., Gendrin, A.,
Gondet, B., Poulet, F., Berthe, M., Soufflot, A., Arvidson, R., Mangold, N.,
Mustard, J., Drossart, P., and Team, O., 2005, Mars surface diversity as
revealed by the OMEGA/Mars Express observations: Science, v. 307, p.
1576-1581.
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C., Wanke, H., Gasnault, O., Hamara, D. K., Janes, D. M., Marcialis, R. L.,
Maurice, S., Mikheeva, I., Taylor, G. J., Tokar, R., and Shinohara, C., 2002,
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Byrne, S., Dundas, C. M., Kennedy,
M. R., Mellon, M. T., McEwen, A. S., Cull, S. C., Daubar, I. J., Shean, D. E.,
Seelos, K. D., Murchie, S. L., Cantor, B. A., Arvidson, R. E., Edgett, K. S.,
Reufer, A., Thomas, N., Harrison, T. N., Posiolova, L. V., and Seelos, F. P.,
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Feldman, W. C., Boynton, W. V., Tokar, R. L.,
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Lawson, S. L., Maurice, S., McKinney, G. W., Moore, K. R., and Reedy, R. C.,
2002, Global distribution of neutrons from Mars: Results from Mars Odyssey:
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Mitrofanov, I., Anfimov, D., Kozyrev, A., Litvak,
M., Sanin, A., Tret'yakov, V., Krylov, A., Shvetsov, V., Boynton, W., Shinohara,
C., Hamara, D., and Saunders, R. S., 2002, Maps of subsurface hydrogen from the
high energy neutron detector, Mars Odyssey: Science, v. 297, p. 78-81.
Mumma,
M. J., Villanueva, G. L., Novak, R. E., Hewagama, T., Bonev, B. P., DiSanti, M.
A., Mandell, A. M., and Smith, M. D., 2009, Strong Release of Methane on Mars in
Northern Summer 2003: Science, v. 323, p. 1041-1045.
Smith, P. H., Tamppari,
L. K., Arvidson, R. E., Bass, D., Blaney, D., Boynton, W. V., Carswell, A.,
Catling, D. C., Clark, B. C., Duck, T., DeJong, E., Fisher, D., Goetz, W.,
Gunnlaugsson, H. P., Hecht, M. H., Hipkin, V., Hoffman, J., Hviid, S. F.,
Keller, H. U., Kounaves, S. P., Lange, C. F., Lemmon, M. T., Madsen, M. B.,
Markiewicz, W. J., Marshall, J., Mckay, C. P., Mellon, M. T., Ming, D. W.,
Morris, R. V., Pike, W. T., Renno, N., Staufer, U., Stoker, C., Taylor, P.,
Whiteway, J. A., and Zent, A. P., 2009, H2O at the Phoenix Landing Site:
Science, v. 325, p. 58-61.
Whiteway, J. A., Komguem, L., Dickinson, C., Cook,
C., Illnicki, M., Seabrook, J., Popovici, V., Duck, T. J., Davy, R., Taylor,
P. A., Pathak, J., Fisher, D., Carswell, A. I., Daly, M., Hipkin, V., Zent,
A. P., Hecht, M. H., Wood, S. E., Tamppari, L. K., Renno, N., Moores, J. E.,
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Precipitation: Science, v. 325, p. 68-70.
Source:
MEPAG Goal IV Science Analysis Group
(2010). “IV. Goal: Prepare for Human Exploration.”
Proposed
replacement text for MEPAG (2008), Mars Scientific Goals, Objectives,
Investigations, and Priorities. Submitted 2 August 2010.